In 2013, the first of several Regional Stream Quality Assessments (RSQA) was done in the Midwest United States. The Midwest Stream Quality Assessment (MSQA) was a collaborative study by the U.S. Geological Survey (USGS) National Water Quality Assessment (NAWQA), the USGS Columbia Environmental Research Center, and the U.S. Environmental Protection Agency (USEPA) National Rivers and Streams Assessment (NRSA). One of the objectives of the RSQA, and thus the MSQA, is to characterize the relationships between water-quality stressors and stream ecology and to determine the relative effects of these stressors on aquatic biota within the streams (U.S. Geological Survey, 2012). To meet this objective, a framework of fundamental geospatial data was required to develop physical and anthropogenic characteristics of the study region, sampled sites and corresponding watersheds, and riparian zones. This dataset represents the 100 water-chemistry sites sampled for the MSQA, and is one of the four fundamental geospatial data layers that were developed for the Midwest study.
One hundred wadeable sites were sampled weekly for contaminants, nutrients, and sediment during the spring and early summer of 2013, half of which were selected by the USEPA using a random or probabilistic sampling design and the other half selected by the USGS using a targeted sampling design. The 50 sites selected by the USEPA were a subset of previously sampled sites from the NRSA Program (U.S. Environmental Protection Agency, 2016); and the 50 sites selected by the USGS were a combination of long-term monitoring sites and newly established sites, characterized as the lesser developed, low-intensity agricultural, and urban sites (Van Metre and others, 2016). Geospatial land-cover information summarized by watershed and riparian zones for candidate targeted sites, in addition to ecology data collected previously at established sites were used to assist in selecting the final targeted sites.
References cited in this document:
Nakagaki, N., Qi, S.L., and Baker, N.T., 2016, Selected environmental characteristics of sampled sites, watersheds, and riparian zones for the U.S. Geological Survey Midwest Stream Quality Assessment: U.S. Geological Survey data release, http://dx.doi.org/10.5066/F77W699S.
U.S. Environmental Protection Agency, 2016, National Rivers and Streams Assessment, accessed July 2016 at https://www.epa.gov/national-aquatic-resource-surveys/nrsa.
U.S. Geological Survey, 2012, The Midwest stream quality assessment: U.S. Geological Survey Fact Sheet 2012-3124, 2 p.
Van Metre, P. C., Frey, J. W., Musgrove, M., Nakagaki, N., Qi, S. L., Mahler, B. J., Wieczorek, M. E., and Button, D. T., 2016, High nitrate concentrations in some Midwest United States streams in 2013 after the 2012 drought: Journal of Environmental Quality v. 45, no. 5, p. 1696-1704, accessed September 10, 2016, at https://dl.sciencesocieties.org/publications/jeq/pdfs/45/5/1696.